1. American Airlines: Founded in 1930, American Airlines is one of the oldest and most significant airlines in the United States. It is headquartered in Fort Worth, Texas. American operates an extensive network, both domestically and internationally, with a large number of flights across the Americas, Europe, Asia, and other regions. The airline is a member of the Oneworld alliance.
  2. Delta Air Lines: Delta is another major American airline headquartered in Atlanta, Georgia. Established in 1924, Delta operates over 5,000 flights per day. It is a member of the SkyTeam alliance and has a strong presence in various domestic and international markets, notably in Europe and Asia.
  3. Southwest Airlines: Founded in 1967, Southwest Airlines is the world's largest low-cost carrier. It is headquartered in Dallas, Texas. Southwest is known for its friendly service and free baggage policies. The airline operates a point-to-point network, primarily serving destinations within the United States, though it has expanded to include some international destinations in the Caribbean and Central America.
  4. United Airlines: Based in Chicago, Illinois, United Airlines was founded in 1926. It is one of the founding members of the Star Alliance. United has an extensive domestic and international network and a significant presence in the Asia-Pacific region.
  5. Alaska Airlines: Headquartered in SeaTac, Washington, Alaska Airlines was founded in 1932. It operates an extensive domestic network, focusing on the West Coast. Alaska is known for its high-quality service and has won numerous awards. In 2016, Alaska acquired Virgin America, expanding its network further.
  6. JetBlue Airways: JetBlue is a major low-cost airline based in New York City. It was founded in 1998 and primarily serves destinations in the United States, though it has expanded to the Caribbean and Latin America. JetBlue is known for its in-flight amenities and high level of service.
  7. Spirit Airlines: Based in Miramar, Florida, Spirit Airlines is an ultra-low-cost carrier founded in 1983. It operates flights throughout the United States, the Caribbean, Mexico, and Latin America. Spirit is known for its a la carte pricing structure, where passengers pay for their options, such as bags and seat selection.
  8. Frontier Airlines: Frontier is an American ultra-low-cost carrier headquartered in Denver, Colorado. Founded in 1994, it operates flights to over 100 destinations in the United States, Canada, Dominican Republic, and Mexico. Like Spirit, Frontier utilizes an a la carte pricing model.
  9. Hawaiian Airlines: Founded in 1929, Hawaiian Airlines is based in Honolulu, Hawaii. It is the largest airline in Hawaii and operates flights between the Hawaiian Islands and destinations in Asia, the South Pacific, and the mainland United States.
  10. Allegiant Air: Allegiant Air is a low-cost airline based in Summerlin, Nevada. It was founded in 1997. Allegiant focuses on flying from smaller airports to popular vacation destinations throughout the United States. It operates an all-Airbus fleet and is known for its unbundled, no-frills service.